Bits per pixel is a measure of the detail for each dot in a picture. A 24 bit picture usually has 8 bits for red, green, and blue. A 32 bit picture adds 8 bits for a transparency value called the alpha value. 8 bits means that the range of color is from 0 to 255.

The DPI is dots per inch. That is how dense the pixels are printed on a page. If your picture is 1000 pixels acrossnad you print it at 300 DPI it takes just 10/3 inches or about 8 cm of paper to print.

The limitations of the human eye, and the monitor, and especially the printer mkae the use of 8 bits reasonable. It is usually possible to rescale the images to different sizes on the printer. Printers have a substantially smaller color range than do monitors. Do not expect the images to be as sharp or clear as they are on the monitor.